CD73, cluster of differentiation 73, is also known as 5′-nucleotidase (5′-NT) or ecto-5′-nucleotidase, is an enzyme serves to convert AMP to adenosine. CD73 catalyzes the formation of extracellular adenosine which contributes to the immunosuppressive tumor environment. CD73 is over-expressed in stromal cells and multiple types of tumor cells, as well as in Tregs, M2 Mφs and myeloid derived suppressor cells (MDSCs).
Preclinical evidence shows that CD73 inhibition prevented adenosine-mediated lymphocyte suppression, increased the activity of CD8+ effector cells, and reduced both MDSCs and Tregs. There are a few anti-CD73 antibodies being developed as potential anticancer agents, but none have been approved for clinical use.